The present invention relates to water softening systems and, more particularly, to an apparatus for, and a method of, reducing total dissolved solids (TDS) in the discharge from the softening system.
Hard water, i.e., water containing certain minerals, such as calcium and magnesium, is undesirable in that these minerals will form a curd when they come in contact with soap, and they will scale in piping, water heaters, pots, washing machines, etc. To alleviate this problem, water softening systems have become quite popular. Such systems convert hard water to soft water by removing minerals, mainly magnesium and calcium, from the hard water. This is done by a process known as positive ion exchange. In this process, sodium or other ions are substituted for calcium and magnesium ions in the hard water.
The process basically involves running hard water through an exchange media, such as polystyrene beads or e.g., zeolite "charged" with positive ions, such as sodium ions or potassium ions. These ions are attracted to the beads due to an inherent negative charge in the beads. A brine, consisting of sodium chloride or potassium chloride dissolved in water, is run over the beads to perform charging. Once the beads are charged, the system is ready to operate by running hard water through the beads. Positive ion exchange thus takes place, and the effluent water is soft.
Eventually, the sodium or potassium ions carried by the beads will be depleted, or virtually depleted. The beads will then need to be recharged with sodium or potassium. The recharging process is the same as the initial charging process in that brine passes over the beads. However, in recharging, any effluent brine now contains magnesium, calcium, and sodium chloride or potassium chloride, as is well known in the art. This recharging process is commonly referred to as regeneration.
The effluent liquid from the regeneration process will have a high degree of what is known as total dissolved solids (TDS), i.e., on the order of 25,000 ppm for an NaCl brine and 22,000 ppm for a KCl brine, much of which will be chlorides. Other elements, such as manganese, iron, sodium, magnesium, and potassium, either naturally existing in the water or collected as a result of water softening, contribute to the TDS of the effluent waste water, as well as chlorides, and thus are present in the 22,000 to 25,000 TDS water.
This high TDS effluent previously has been sent through a drain to the sewer system as any drain water from a house, office, etc. Due to recent environmental concerns and the desire for water reclamation, many municipalities are enacting or considering ordinances limiting the amount of chlorides and/or TDS that can be sent through sewer systems. These limits often are on the order of 250 ppm chlorides and 500 ppm TDS. Since effluent in the regeneration process far exceeds this typical maximum acceptable amount, water softeners have often been flat out banned by some municipalities.
Even if such softeners are not banned, costly service is required to meet the minimum ppm requirements. Such service typically involves service personnel periodically traveling to the houses or offices having water softeners, removing the tanks with the used beads, and replacing them with tanks of charged beads. The tanks with the used beads are taken to a facility for a centralized regeneration process. Once regenerated, these tanks of beads can again be used to replace other tanks with used beads.
Therefore, there is a great need for a water conditioning system that meets TDS requirements.